388 research outputs found
Software for Exact Integration of Polynomials over Polyhedra
We are interested in the fast computation of the exact value of integrals of
polynomial functions over convex polyhedra. We present speed ups and extensions
of the algorithms presented in previous work. We present the new software
implementation and provide benchmark computations. The computation of integrals
of polynomials over polyhedral regions has many applications; here we
demonstrate our algorithmic tools solving a challenge from combinatorial voting
theory.Comment: Major updat
Coefficients of Sylvester's Denumerant
For a given sequence of positive integers, we consider
the combinatorial function that counts the nonnegative
integer solutions of the equation , where the right-hand side is a varying
nonnegative integer. It is well-known that is a
quasi-polynomial function in the variable of degree . In combinatorial
number theory this function is known as Sylvester's denumerant.
Our main result is a new algorithm that, for every fixed number , computes
in polynomial time the highest coefficients of the quasi-polynomial
as step polynomials of (a simpler and more explicit
representation). Our algorithm is a consequence of a nice poset structure on
the poles of the associated rational generating function for
and the geometric reinterpretation of some rational
generating functions in terms of lattice points in polyhedral cones. Our
algorithm also uses Barvinok's fundamental fast decomposition of a polyhedral
cone into unimodular cones. This paper also presents a simple algorithm to
predict the first non-constant coefficient and concludes with a report of
several computational experiments using an implementation of our algorithm in
LattE integrale. We compare it with various Maple programs for partial or full
computation of the denumerant.Comment: minor revision, 28 page
Linear vector optimization and European option pricing under proportional transaction costs
A method for pricing and superhedging European options under proportional
transaction costs based on linear vector optimisation and geometric duality
developed by Lohne & Rudloff (2014) is compared to a special case of the
algorithms for American type derivatives due to Roux & Zastawniak (2014). An
equivalence between these two approaches is established by means of a general
result linking the support function of the upper image of a linear vector
optimisation problem with the lower image of the dual linear optimisation
problem
Finding the "truncated" polynomial that is closest to a function
When implementing regular enough functions (e.g., elementary or special
functions) on a computing system, we frequently use polynomial approximations.
In most cases, the polynomial that best approximates (for a given distance and
in a given interval) a function has coefficients that are not exactly
representable with a finite number of bits. And yet, the polynomial
approximations that are actually implemented do have coefficients that are
represented with a finite - and sometimes small - number of bits: this is due
to the finiteness of the floating-point representations (for software
implementations), and to the need to have small, hence fast and/or inexpensive,
multipliers (for hardware implementations). We then have to consider polynomial
approximations for which the degree- coefficient has at most
fractional bits (in other words, it is a rational number with denominator
). We provide a general method for finding the best polynomial
approximation under this constraint. Then, we suggest refinements than can be
used to accelerate our method.Comment: 14 pages, 1 figur
Studying Wythoff and Zometool Constructions using Maple
We describe a Maple package that serves at least four purposes. First, one
can use it to compute whether or not a given polyhedral structure is Zometool
constructible. Second, one can use it to manipulate Zometool objects, for
example to determine how to best build a given structure. Third, the package
allows for an easy computation of the polytopes obtained by the kaleiodoscopic
construction called the Wythoff construction. This feature provides a source of
multiple examples. Fourth, the package allows the projection on Coxeter planesComment: 11 pages, 11 figure
Faster Geometric Algorithms via Dynamic Determinant Computation
The computation of determinants or their signs is the core procedure in many
important geometric algorithms, such as convex hull, volume and point location.
As the dimension of the computation space grows, a higher percentage of the
total computation time is consumed by these computations. In this paper we
study the sequences of determinants that appear in geometric algorithms. The
computation of a single determinant is accelerated by using the information
from the previous computations in that sequence.
We propose two dynamic determinant algorithms with quadratic arithmetic
complexity when employed in convex hull and volume computations, and with
linear arithmetic complexity when used in point location problems. We implement
the proposed algorithms and perform an extensive experimental analysis. On one
hand, our analysis serves as a performance study of state-of-the-art
determinant algorithms and implementations. On the other hand, we demonstrate
the supremacy of our methods over state-of-the-art implementations of
determinant and geometric algorithms. Our experimental results include a 20 and
78 times speed-up in volume and point location computations in dimension 6 and
11 respectively.Comment: 29 pages, 8 figures, 3 table
Toric Methods in F-theory Model Building
In this review article we discuss recent constructions of global F-theory GUT
models and explain how to make use of toric geometry to do calculations within
this framework. After introducing the basic properties of global F-theory GUTs
we give a self-contained review of toric geometry and introduce all the tools
that are necessary to construct and analyze global F-theory models. We will
explain how to systematically obtain a large class of compact Calabi-Yau
fourfolds which can support F-theory GUTs by using the software package PALP.Comment: 19 pages. Prepared for the special issue "Computational Algebraic
Geometry in String and Gauge Theory" of Advances in High Energy Physics, v2:
references added, typos correcte
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